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There is just something about procellarids — the petrels, shearwaters, and allies. Perhaps it is their gliding flight over the waves, covering huge distances without apparent effort. Perhaps it is the apparent mastery of the wildest winds and seas — a
Pterodroma
arcing over the horizon is the epitome of the untamed ocean realm and the classic seabird. An example is
Murphy's Petrel
(above), shown here a hundred miles off the California coast, arcing over the waves in a gale.

Perhaps it is awe for their incredible transequatorial migrations, knowing that a bird seen in the Gulf of Alaska was nesting in the Southern Hemisphere just a month or so before.
Buller's Shearwater
(left and below left ; the latter with Pink-footed Shearwaters) nests in New Zealand and then undertakes a great clockwise migration around the north Pacific, reaching Monterey Bay (as in this photo) every August-September. There is feeds on the rich resources brought to the surface by deep-water upwelling. Buller's mix with
Pink-footed Shearwater
(below left), a species whose primary breeding grounds are in the Juan Fernandez Islands off the west coast of Chile. And here to is
Sooty Shearwater
(below right) — up to half-a-million in season — in the midst of a huge figure-8 migration route that averages 64,000 km [=40,000 miles] annually. These data are from miniaturized archival tags that tracked Sooty Shearwaters from New Zealand breeding grounds to feeding areas off Japan, Alaska, and California in what the researchers called an integration of "oceanic resources across the Pacific Ocean in an endless summer" (Shaffer et al. 2006). This is the longest animal migration ever tracked. At times a shearwater traveled up to 620 miles (1000 km) a day.

Yet another reason to be fascinated by procellarids is that we (usually) must venture away from our land habitat into the open ocean to observe them. We rarely see them well from a constantly moving boat. But at certain sea-watching points huge numbers of procellarids can be seen from shore. One of those is Pt. Pinos at the tip of the Monterey Peninsula, just a few blocks from my home (two photos above right). The photo above the sea-watchers shows a dozen
Black-vented Shearwater
headed west, past Pt. Pinos, on a windy day in December. During my 1.5 hour of sea-watching they were passing by at the rate of at least 100/minute, or 9000 in that short period. Eleven species of the Procellariidae have been observed from Pt. Pinos, including 3 vagrant
Pterodroma
(Cook's, Hawaiian, and Mottled).

Just about 30% of procellarids are shearwaters (genera
Ardenna, Puffinus, Calonectris
). Aside from a handful of prions, fulmars and giant-petrels, the majority are petrels in 8 genera. Some 32 species are
Pterodroma
petrels, the really far-out procellarids ranging thousands of miles offshore. In the Indian Ocean is
Barau's Petrel
(right). Very little is known about its life at sea. It breeds only on the Mascarene Islands; this adult is heading ashore on Réunion I. late in the afternoon. Virtually all procellarids breed on offshore islands, many of them using burrows or caves. Dogs, cats, rats, weasels and the like are death of breeding adults and their young. Because there are so few predator-free islands, procellarids have declined in many places globally.

Yet another aspect of procellarids that makes them fascinating is that a fair number are difficult to identify at sea, and there has been a progression of knowledge in recent years as one after another seemingly intractable problem is worked out. I even had a hand in sorting out the identification issues in the small black-and-white shearwaters (Roberson 1996) and in the the seven tiny
Pterodroma
petrels in the tropical Pacific collectively known as the
'Cookilaria'
petrels (Roberson & Bailey 1991). During four months at sea as a seabird researcher about the
USS MacArthur
on a NOAA tuna-porpoise research cruise in fall 1989, I gained firsthand experience with five of the
'Cookilaria.'
On my return I received a Chapman grant to travel to the American Museum of Natural History in New York to examine collection, take measurements (below left; measuring the bill of a Cook's Petrel specimen), and working with Keith Hansen in his i.d. plate for publication (below right).

As all my experience for writing about
Pterodroma
petrels came from trips off California, and the eastern tropical Pacific cruise, it was really nice to do a New Zealand pelagic trip in 2009 — and now with a digital camera! One could even take nice detailed photos of
Cook's Petrel
(above left). And because we encounter petrels almost always in the open ocean — out of sight of land — is always dramatic to see a petrel flying toward a remote breeding island. Here (above right), a Cook's heads towards Little Barrier Island in the Haurake Gulf.

There are two species of Giant Petrel on earth: this one, set against the snowy landscape of South Georgia Island, is Southern Giant-Petrel (lovely shot by Greg W. Lasley during an Antarctic cruise). Many of the breeding island for petrels and shearwaters are difficult to reach.

There are six species of prions — plus the tiny Blue Petrel
Halobaena caerulea
— that pose challenges for those on Antarctic and sub-Antarctic cruises.
Fairy Prion
(left) may be encountered on a New Zealand pelagic trip. It is found farther north than most.

My Haurake Gulf pelagic also had a
Common Diving-Petrel
(above left). Until very recently, the four species of diving-petrels were assigned to a separate family, the Pelecanoididae. In the massive molecular review by Prum et al. (2015), using multiple nuclear and mtDNA introns, it was shown that the diving-petrels in genus
Pelecanoides
are embedded within the phylogeny of the petrels and shearwaters. Thus the old "family" must now be merged into the Procellariidae. There are two circumpolar species, one in the sub-Antarctic and another in more temperate (but still quite cold) southern waters (this is the Common Diving-Petrel of New Zealand and Tasmania, shown above left). The other two species are from South America, including
Peruvian Diving-Petrel
(above right). All the diving-petrels resemble each other closely, and are separated on details of breadth and length of their stout bills, plus details of the distribution of whitish on underparts or face. Although diving-petrels are clearly in the Order Procellariiformes, having "tube-noses" as do albatrosses, shearwaters, and storm-petrels, most of the Procellariiformes are masters of the air, gliding for hours above the waves. Diving-petrels are better adapted for the sea. They have stocky bodies with short wings and thick necks, and fly with whirling wingbeats. In this they quite resemble the completely unrelated auks and relatives (Alcidae) of the northern hemisphere. This is a case of convergent evolution. They are agile swimmers and divers, even in the roughest of seas, and in this they again resemble the auks or penguins. Like alcids, they ride rather buoyantly on the water surface when not diving. Diving-petrels are generally found singly or in loose groups on the ocean, but they breed in dense colonies, mostly on offshore islands with only a few mainland colonies in protected areas. Nests are in burrows and, as with many colonial seabirds, they arrive and depart those burrows at night to avoid predators. Diving-petrels tend to feed inshore and rarely disperse far from the breeding colonies, although a few individuals have been encountered a fair distance offshore (Carboneras 1992).

Perhaps the most desired offshore birds are Pterodroma petrels. Off the Atlantis coast of North America, the regular species is
Black-capped Petrel
(left). Recently the fact that there are two "types" of Black-capped Petrel has been publicized. "Light morph" types predominated, such as the one at left with broad while collar, but there were some "dark" or "intermediate" types (above) with dingy collars. This variation has recently been quantified (Howell & Patteson 2008b) but it is not known whether it is related to specific island populations.

Variation in Cory's Shearwater is also evident, and is related to specific island populations. The most common were "Atlantic" Cory's Shearwater
C. d. borealis
: a huge, hulking shearwater with white underwings but all-dark remiges (below left). A very few were slightly smaller birds with more buoyant flight and (often) a scaly back, and a different underwing pattern. The most prominent example was one that followed the boat (below right) with prominent white 'fingers' in the underwings, including the outermost primaries. This is the Mediterranean breeding "Scopoli's Shearwater"
C. d. diomedea
, sometimes considered a separate species; identification is discussed in Gutiérrez (1998) and Howell & Patteson (2008a).

Another reasonable common species off the eastern U.S. coast is Audubon's Shearwater (right). It breeds in the Caribbean and ranges northward in the Gulf Stream. In the Pacific, the populations in the Galapagos Islands have recently been split as Galapagos Shearwater
Puffinus subalaris
.

In the Atlantic Ocean, observers have just recently discovered that Fea's Petrel
P. feae
, Trindade Petrel
P. arminjoniana
(the Atlantic Ocean version of now-split Herald Petrel
P. heraldica
), and even the endangered Bermuda Petrel
P. cahow
may be regular in summer. Their identification has just recently been understood (Tove 1997, Wingate et al. 1998). Here's a Trindade Petrel (below) in a high arc over the Gulf Stream off North Carolina in May.

In the North Pacific we have learned in the past 25 years that Cook's Petrel and Murphy's Petrel
P. ultima
are apparently regular well offshore, that both Mottled
P. inexpectata
and Stejneger's
P. longirostris
are likely regular in migration way out there (see McCaskie & Roberson 1992 for details of the first record of the latter species), and Great-winged Petrel
P. macroptera
visits on occasion. Indeed, I found during a research cruise in April 1991 well offshore between Pt. Sur to Pt. Año Nuevo, California, in very rough weather, that Murphy's Petrel (left) was the commonest bird out there beyond 50 miles offshore (at least that year).

While Cook's and Murphy's are southern petrels that get to the north Pacific regularly, others are vagrants. So fair it appears that Cape Petrel (below left) never gets north of the Galapagos but another large southern species, White-chinned Petrel (below right, photographed off South Africa) is a vagrant to both coasts of North America. This particular White-chinned Petrel has an unusual amount of white on the head.

Carboneras (1992) begins his discussion of this family by saying: "The taxonomy of the Procellariidae is extraordinarily complex, and it is consequently subject to frequent revisions, and more than its fair share of polemic." One example is the "Dark-rumped Petrels" now split as
Galapagos Petrel
(below left) and
Hawaiian Petrel
(below right, a superb shot by Peter J. Dunn). It took decades to split the two taxa into separate species, and another decade or so before observers accepted the fact that it was Hawaiian Petrel that occurs in offshore California. Peter Dunn's photo of Hawaiian Petrel is so dramatic because it shows the Pt. Pinos Lighthouse in the background! These
Pterodroma
are usually found only many miles offshore!

The above pair of photos nicely illustrate difference between Galapagos Petrel (photo from the Galapagos) and Hawaiian Petrel (photo in California). Note the heavy bill and 'shawl' over the entire rear of the head on Galapagos Petrel. Hawaiian Petrel has a decidedly shorter, smaller bill and much reduced 'shawl' restricted to the rear of the crown, and set off by a white indentation behind the eye (see Force et al. 2005, Howell 2012).

Another example of contention in taxonomy and identification is among the small black-and-white shearwaters in the genus
Puffinus
. Murphy (1952) lumped many around the world as "Manx Shearwater
P.
puffinus
." This was well wide of the mark and the modern trend is to separate isolated island populations in different oceans as distinct species. But even then there remains debate: should Newell's Shearwater
P. newelli
in Hawaii be lumped with Townsend's Shearwater
P. auricularis
of the Revillagigedos Is., Mexico? Jehl (1982) argued they should be lumped (mostly on vocalizations) but most recent authors do not agree; see Howell et al. (1994), Howell (2015). The AOU did not spilt Townsend's and Newell's into two species until 2015.

These taxonomic issues sometimes overshadow the truly impressive range expansion in the last half-century by the Manx Shearwater of the North Atlantic. Once restricted as a breeding species to islands off nw. Europe (Scotland, etc.) it first colonized northeastern North America and then began an explosion of vagrancy that took birds all the way to New Zealand and Australia (see Kinsky & Fowler 1973 for details of a bird banded in Britain being picked up in Australia). The first vagrants to the n.e. Pacific were in the late 1970s; by the 1990s Manx Shearwater had become a regular migrant and winterer in small numbers in Monterey Bay. They must be nesting somewhere around the Gulf of Alaska now as we see young birds in the fall ( more details in Roberson 1996). This is as impressive a range expansion as any species on earth!

There are several good papers on the identification of Manx Shearwater; Howell et al. (1994), Roberson (1996). The two photos below from Monterey Bay show some classic
Manx Shearwater
features: sharply demarcated face pattern with an 'ear-surround' and white undertail coverts (below left, nice shot by Brian L. Sullivan), and on a bird going away (below right), the white flanks extend upwards to sides of rump. Note in both shots crisp blackish above/white below pattern and short-tailed appearance.

The influence of water temperature and salinity conditions on distribution is important; some aspects for the northeast Pacific have been summarized by Ainley (1976) and Briggs et al. (1987). Vagrancy among procellarids is indeed impressive, and was recognized a few decades ago by Bourne (1967); I co-authored a paper on the second state record of Streaked Shearwater
Calonectris leucomelas
(Roberson et al. 1977) and California's first Wedge-tailed Shearwater (Stallcup et al. 1988). A substantial amount of wandering is influenced by conditions on a global scale. El Niño-Southern Oscillation conditions greatly impact bird distribution when they occur, and the "great" El Niños (like 1982–1983 and 1997–1998) engender distant incursions of warm water species, sometimes for years afterwards until a more "typical" balance is restored. The occurrence of Wedge-tailed Shearwater off California appears to be linked to El Niño; this dark morph was in Monterey Bay for several weeks in October 1998 (right).

I haven't even touched on breeding biology or foraging ecology. Many details are packed into Warham (1995) and summarized by Carboneras (1992). But I did want to mention the amazing interaction between some petrels and cetaceans. Juan Fernandez Petrels and Wedge-tailed Shearwaters are among the foraging seabirds regularly found around tuna-porpoise assemblages in the eastern tropical Pacific (see Au & Pitman 1986). My four months at sea in 1989 included studying these associations.

Even more specific and dramatic is evidence that the New Zealand breeding Parkinson's Petrel (above) consistently forages with pods of Melon-headed Whale
Peponocephala electra
and False Killer Whale
Pseudorca crassidens
in the tropical Pacific. Nearly two-thirds of all observations on multiple research cruises were in direct association with these two species (Pitman & Ballance 1992).

On my cruise in fall 1989, I noticed that the few Phoenix Petrels seen were often associated with large cetaceans. Below is my shot of a Phoenix Petrel in the wake of an Orca (Killer Whale) way offshore in the eastern tropical Pacific.

Photos
: The
Murphy's Petrel
Pterodroma ultima
was well offshore central California on 11 Apr 1991. The
Buller's Shearwater
Ardenna bulleri
was on Monterey Bay on 29 Oct 2011; the mixed flock of a Buller's and several
Pink-footed Shearwater
A. creatopus
was there on 23 Sep 2012, and the
Sooty Shearwater
A. griseus
was taken on 13 Sep 2014. The photo of 20
Black-vented Shearwater
Puffinus opisthomelas
passing Pt. Pinos, California, was taken 23 Dec 2015; the photos of birders watching seabirds from Pt Pinos were from Apr 2005 (left) and Nov 2015 (right). The
Barau's Petrel
Pterodroma baraui
were at the St. Etienne R. mouth, Réunion I., Indian Ocean, on 9 Dec 1992. Although the
Cook's Petrel
Pterodroma cookii
specimen illustrates the discussion of the AMNH research that led to the paper with
Keith Hansen's
fine painting, the actual specimen shown here is at California Academy of Science, San Francisco, and it represents the first specimen record for California (found ashore in Santa Cruz 17 Nov 1983; #CAS71447). The photos of
Cook's Petrel
at sea were in the Hauraki Gulf, New Zealand, on 14 Nov 2009, as were the shots of
Fairy Prion
Pachyptila turtur
and
Common Diving-Petrel
Pelecanoides urinatrix
. The
Southern Giant-Petrel
Macronectes giganteus
was photographed by Greg W. Lasley off South Georgia I., South Atlantic Ocean, on 26 Jan 1999. The photo of
Peruvian Diving-Petrel
Pelecanoides gamotii
was taken just off the Paracas Peninsula, Peru, from a small boat on 12 June 1987. The
Black-capped Petrel
Pterodroma hasitata
was off Cape Hatteras, North Carolina, on 13 June 2009, as was the
"Scopoli's" Cory's Shearwater
Calonectris d. diomedea
, and the
Audubon's Shearwater
Puffinus lherminirei
; the photo of
"Atlantic" Cory's Shearwater
C. d. borealis
: was taken the next day. The
Trindade Petrel
Pterodroma arminjoniana
was off Cape Hatteras, North Carolina, on 26 May 2013;
Murphy's Petrel
P. ultima
was off central California in April 1991. The
Cape Petrel
Daption capense
was off Cape Town, South African, on 4 July 2005, as was the
White-chinned Petrel
Procellaria aequinoctialis
. The
Galapagos Petrel
Pterodroma phaeopygia
was between Isabella & Santa Cruz Is., Galapagos, on 23 Sep 1989. Peter J. Dunn photographed the
Hawaiian Petrel
Pterodroma sandwichensis
from a boat just off Pt. Pinos, Monterey Co., California, on 25 Aug 2014. Brian L. Sullivan photographed the left-hand
Manx Shearwater
Puffinus puffinus
on Monterey Bay, California, on 11 Sep 2011; the right-hand bird was there on 10 Oct 2015. The dark-morph
Wedge-tailed Shearwater
Ardenna pacifica
was on Monterey Bay on 11 Oct 1998. The
Parkinson's Petrel
Procellaria parkinsoni
was in the Hauraki Gulf, New Zealand, on 14 Nov 2009. The interaction between
Phoenix Petrel
Pterodroma alba
and
Orca
Orcinus orca
was at 7°30'N, 144°30'W, on 5 Sep 1989.

There are many seabird books but apparently none that can strictly be called a family book on the Petrels, Shearwaters and allies. A nice introduction to the family, with a selection of photos, is in Carboneras (1992). There is much to glean from the beautifully written prose in Murphy (1936) but it is limited to the waters off South America. Warham (1995) summarizes behavior and physiology but does not do so species-by-species; it is not a "family book." Photographs of all species are in Harrison (1987) and in Enticott & Tipling (1998), and art and text in Harrison's earlier work (Harrison 1983). Harrison's efforts were monumental for their time but one must now be very careful in using the text (especially of the earlier book) which is riddled with errors. For many years the sea-birder could not rely on any standard text for shearwaters and petrels. Information about taxonomy, distribution, and identification is being learned and revised so quickly that books are often out-of-date by the time they are published (e.g., Carboneras 1992, Enticott & Tipling 1998) and a good local text was often best. In the Monterey Bay area useful literature on seabirds (including all the shearwaters) were by Stallcup (1976, 1990). For the difficult groups, published papers were often critical. For North Atlantic
Pterodromas
, Tove (1997) and Wingate et al. (1998) were a must. For the
'Cookilaria'
Pterodromas
of the Pacific, Roberson & Bailey (1991) was good. For dark
Pterodromas
of the Pacific, Bailey et al. (1989) was good. For tips on separating the Tahiti/Phoenix petrels and on other tropical Pacific problems, see Spear et al. (1992). On the small black-and-white shearwaters of the eastern Pacific, one must read Howell et al. (1994) or Roberson (1996). I am not as well-versed in the literature of Australasian and subantarctic problems but, as in the northern hemisphere, I suspect the real gold lies in articles and papers and not in books published to date.
Much more recently, two excellent books have appeared that cover many of the petrels and shearwaters: Shirihai (2007), for the Antarctic and subAntarctic Oceans, and Howell (2015), covering both the Pacific and Atlantic procellarids that have reached North America (including many vagrants). These are very up-to-date on identification and distributional issues, with many excellent photos. This still leaves some tropical species uncovered in the detail now available for North America and the Antarctic.

Harrison, P. 1987. Seabirds of the World: a Photographic Guide. Bromley, England: Christopher Helm. [Published in the U.S. as Field Guide to the Seabirds of the World, Lexington, MA.: Stephen Greene Press]